This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. he purpose of the project, which is ongoing, is to study 48 pairs of monozygotic twins using a longitudinal cotwin-control design to assess effects of alcohol and drug use on brain structure and function. The project uses a comprehensive and complementary battery of neuropsychological, psychophysiological and MRI assessment. MRI imaging includes high-resolution structural imaging for morphometric analyses and whole-brain functional imaging during performance of a task shown to be sensitive to reward-sensitive neural areas.